The site specific delivery of drugs to in vivo sites can increase the therapeutic effectiveness of drugs while reducing non-specific toxic effects. The use of thermolabile vesicles for the delivery of drugs to specific sites is a potentially potent method for improving the specificity of drug chemotherapy in cancer and other diseases. Previous reports have demonstrated the validity of the approach as well as the ability to formulate vesicles with sharp (1-3 C) phase transitions. The proposed work would attempt to optimize these formulations to produce the sharp phase transition in the range 38-40 C. This Phase I effort will also attempt to demonstrate that encapsulated material is rapidly released during the phase transition, and, in a preliminary manner, demonstrate that vesicle-encapsulated material is maintained in circulation for prolonged periods and released at sites of externally-induced hyperthermia. In biomedical applications, thermolabile vesicles formulations can be used to deliver pharmaceuticals and chemotherapeutics to specific sites with reduced toxicity to other parts of the body.